Extravascular implantable electrical lead having undulating configuration

ABSTRACT

This disclosure describes an implantable medical electrical lead and an ICD system utilizing the lead. The lead includes a lead body defining a proximal end and a distal portion, wherein at least a part of the distal portion of the lead body defines an undulating configuration. The lead includes a defibrillation electrode that includes a plurality of defibrillation electrode segments disposed along the undulating configuration spaced apart from one another by a distance. The lead also includes at least one electrode disposed between adjacent sections of the plurality of defibrillation sections. The at least one electrode is configured to deliver a pacing pulse to the heart and/or sense cardiac electrical activity of the heart.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/963,303, filed on Dec. 9, 2015 (now U.S. Pat. No. 10,675,478, issuedon Jun. 9, 2020), which claims the benefit of both U.S. ProvisionalApplication No. 62/089,417, filed on Dec. 9, 2014 and U.S. ProvisionalApplication No. 62/262,408, filed on Dec. 3, 2015, the entire content ofeach is incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present application relates to electrical stimulation leads and,more particularly, electrical stimulation leads having an undulatingconfiguration for improved defibrillation, sensing, and/or pacingcapabilities for use in extracardiovascular applications (e.g.,subcutaneous or substernal applications).

BACKGROUND OF THE INVENTION

Malignant tachyarrhythmia, for example, ventricular fibrillation, is anuncoordinated contraction of the cardiac muscle of the ventricles in theheart, and is the most commonly identified arrhythmia in cardiac arrestpatients. If this arrhythmia continues for more than a few seconds, itmay result in cardiogenic shock and cessation of effective bloodcirculation. As a consequence, sudden cardiac death (SCD) may result ina matter of minutes.

In patients with a high risk of ventricular fibrillation, the use of animplantable cardioverter defibrillator (ICD) system has been shown to bebeneficial at preventing SCD. An ICD system includes an ICD that is abattery powered electrical shock device, that may include an electricalhousing electrode (sometimes referred to as a can electrode), that iscoupled to one or more electrical lead wires placed within the heart. Ifan arrhythmia is sensed, the ICD may send a pulse via the electricallead wires to shock the heart and restore its normal rhythm. Owing tothe inherent surgical risks in attaching and replacing electrical leadsdirectly within or on the heart, subcutaneous ICD systems have beendevised to provide shocks to the heart without placing electrical leadwires within the heart or attaching electrical wires directly to theheart.

Electrical leads being utilized in subcutaneous systems typicallyinclude linear or curvilinear arrays of electrodes positioned on thelead body. Thus, the delivery of electrical stimulation therapy to theheart with current lead designs provides limited therapy vectorsdepending on the shape of the lead body, for which the electrical energymay impact the heart.

SUMMARY

This disclosure describes an implantable medical electrical lead and anICD system utilizing the lead. The lead includes a lead body defining aproximal end and a distal portion, wherein at least a part of the distalportion of the lead body defines an undulating configuration. The leadincludes a defibrillation electrode that includes a plurality ofdefibrillation electrode segments disposed along the undulatingconfiguration spaced apart from one another by a distance. The lead alsoincludes at least one electrode disposed between adjacent sections ofthe plurality of defibrillation sections. The at least one electrode isconfigured to deliver a pacing pulse to the heart and/or sense cardiacelectrical activity of the heart.

In some instances, the plurality of defibrillation electrode segmentsare disposed along at least 80% of undulating configuration. In otherinstances, the plurality of defibrillation electrode segments aredisposed along at least 90% of undulating configuration. The undulatingconfiguration may include a plurality of peaks with a first portion ofthe plurality of peaks extending in a first direction away from a majorlongitudinal axis of the lead and a second portion of the plurality ofpeaks extending in a second, opposite direction away from the majorlongitudinal axis of the lead. The plurality of defibrillation electrodesegments may, in some examples, be disposed along the first portion ofthe plurality of peaks and the at least one electrode may be disposed onthe second portion of the plurality of peaks. In another example, theplurality of defibrillation electrode segments are disposed along atleast one of the first and second portions of peaks and the at least oneelectrode is disposed along a segment of the undulating portion betweenpeaks.

This application also provides an extravascular implantablecardioverter-defibrillator (ICD) system comprising an extravascularelectrical stimulation lead and an ICD coupled to the extravascularelectrical stimulation lead. The electrical stimulation lead includes alead body defining a proximal end and a distal portion, wherein at leasta part of the distal portion of the lead body defines an undulatingconfiguration. The lead includes a defibrillation electrode thatincludes at least a first defibrillation electrode segment and a seconddefibrillation electrode segment disposed along the undulatingconfiguration spaced apart from one another by a distance. The lead alsoincludes at least one electrode disposed between the first and seconddefibrillation segments, the at least one electrode configured to, atleast one of, deliver a pacing pulse to the heart and sense cardiacelectrical activity of the heart.

This application also provides a method for implanting an extravascularelectrical stimulation lead within a substernal location of a patient.The method includes creating an incision near a center of the torso ofthe patient, introducing an implant tool into the substernal locationvia the incision, and advancing the implant tool within the substernallocation from the incision superior along a posterior of a sternum toform a substernal path. The method further includes introducing a distalportion of the lead into the substernal location. The lead includes alead body defining a proximal end and the distal portion, wherein atleast a part of the distal portion of the lead body defines a pre-formedundulating configuration, a defibrillation electrode that includes aplurality of defibrillation electrode segments disposed along theundulating configuration spaced apart from one another by a distance,and at least one electrode disposed between adjacent segments of theplurality of defibrillation segments, the at least one electrodeconfigured to, at least one of, deliver a pacing pulse to the heart andsense cardiac electrical activity of the heart. The method includesadvancing the distal portion of the lead through the substernal path,wherein the undulating configuration of the lead is in a relativelystraight configuration when being advanced through the substernal path,and withdrawing the implant tool toward the incision to remove theimplant tool from the body while leaving the lead in place along thesubsternal path. The distal portion of the lead takes its pre-formedundulating configuration within the substernal location as it exist theimplant tool. The at least one electrode is disposed on the undulatingconfiguration such that that undulating configuration pushes the atleast one electrodes toward the left side of sternum compared todefibrillation electrode segments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a front view of a patient implanted with theextracardiovascular ICD system implanted intra-thoracically.

FIG. 1B is a side view of the patient implanted with theextracardiovascular ICD system implanted intra-thoracically.

FIG. 1C is a transverse view of the patient implanted with theextracardiovascular ICD system implanted intra-thoracically.

FIG. 2 is a front view of a patient implanted with theextracardiovascular ICD system implanted extra-thoracically.

FIG. 3A is a schematic diagram illustrating an example lead constructedin accordance with the principles of the present application.

FIG. 3B is a schematic diagram illustrating an side view of the distalportion of the example lead of FIG. 3A.

FIG. 4 is a schematic diagram illustrating another example leadconstructed in accordance with the principles of the presentapplication.

FIG. 5 is a schematic diagram illustrating a further example leadconstructed in accordance with the principles of the presentapplication.

FIG. 6 is a schematic diagram illustrating another example leadconstructed in accordance with the principles of the presentapplication.

FIG. 7 is a schematic diagram illustrating another example leadconstructed in accordance with the principles of the presentapplication.

FIG. 8 is a schematic diagram illustrating another example leadconstructed in accordance with the principles of the presentapplication.

FIG. 9 is a schematic diagram illustrating another example leadconstructed in accordance with the principles of the presentapplication.

FIG. 10 is a functional block diagram of an example configuration ofelectronic components of an example ICD, such as the ICD of the systemin FIGS. 1A, 1C, and 2 .

DETAILED DESCRIPTION

As used herein, relational terms, such as “first” and “second,” “over”and “under,” “front” and “rear,” and the like, may be used solely todistinguish one entity or element from another entity or element withoutnecessarily requiring or implying any physical or logical relationshipor order between such entities or elements.

Referring now to the drawings in which like reference designators referto like elements, there is shown in FIGS. 1A-C and FIG. 2 are conceptualdiagrams illustrating various views of an exemplary extracardiovascularimplantable cardioverter-defibrillator (ICD) system 8. ICD system 8includes an ICD 9 connected to a medical electrical lead 10 constructedin accordance with the principles of the present application. FIG. 1A isa front view of a patient implanted with the extracardiovascular ICDsystem 8. FIG. 1B is a side view of the patient implanted with theextracardiovascular ICD system 8. FIG. 1C is a transverse view of thepatient implanted with the extracardiovascular ICD system 8.

The ICD 9 may include a housing that forms a hermetic seal that protectscomponents of the ICD 9. The housing of the ICD 9 may be formed of aconductive material, such as titanium or titanium alloy, which mayfunction as a housing electrode (sometimes referred to as a canelectrode). In other embodiments, the ICD 9 may be formed to have or mayinclude one or more electrodes on the outermost portion of the housing.The ICD 9 may also include a connector assembly (also referred to as aconnector block or header) that includes electrical feedthroughs throughwhich electrical connections are made between conductors of lead 10 andelectronic components included within the housing of the ICD 9. As willbe described in further detail herein, housing may house one or moreprocessors, memories, transmitters, receivers, sensors, sensingcircuitry, therapy circuitry, power sources and other appropriatecomponents. The housing is configured to be implanted in a patient, suchas the patient.

ICD 9 is implanted extra-thoracically on the left side of the patient,e.g., under the skin and outside the ribcage (subcutaneously orsubmuscularly). ICD 9 may, in some instances, be implanted between theleft posterior axillary line and the left anterior axillary line of thepatient. ICD 9 may, however, be implanted at other extra-thoraciclocations on the patient as described later.

FIGS. 3A and 3B are schematic diagrams illustrating various views oflead 10 in further detail. The lead 10 may include an elongated leadbody 12 sized to be implanted in an extracardiovascular locationproximate the heart, e.g., intra-thoracically (as illustrated in FIGS.1A-C) or extra-thoracically (as illustrated in FIG. 2 ). For example,the lead 10 may extend extra-thoracically under the skin and outside theribcage (e.g., subcutaneously or submuscularly) from ICD 9 toward thecenter of the torso of the patient, for example, toward the xiphoidprocess of the patient. At a position proximate xiphoid process, thelead body 12 may bend or otherwise turn and extend superiorly. In theexample illustrated in FIGS. 1A-C, the lead body 12 extends superiorlyintra-thoracically underneath the sternum, in a direction substantiallyparallel to the sternum. In one example, the distal portion 16 of lead10 may reside in a substernal location such that distal portion 16 oflead 10 extends superior along the posterior side of the sternumsubstantially within the anterior mediastinum 36. Anterior mediastinum36 may be viewed as being bounded laterally by pleurae 39, posteriorlyby pericardium 38, and anteriorly by the sternum 22. In some instances,the anterior wall of anterior mediastinum 36 may also be formed by thetransversus thoracis and one or more costal cartilages. Anteriormediastinum 36 includes a quantity of loose connective tissue (such asareolar tissue), adipose tissue, some lymph vessels, lymph glands,substernal musculature (e.g., transverse thoracic muscle), the thymusgland, branches of the internal thoracic artery, and the internalthoracic vein. In another example, e.g., illustrated in FIG. 2 , thelead body 12 may extend superiorly extra-thoracically (instead ofintra-thoracically), e.g., either subcutaneously or submuscularly abovethe ribcage/sternum. The lead 10 may be implanted at other locations,such as over the sternum, offset to the right of the sternum, angledlateral from the proximal or distal end of the sternum, or the like.

The lead body 12 may have a generally tubular or cylindrical shape andmay define a diameter of approximately 3-9 French (Fr), however, leadbodies of less than 3 Fr and more than 9 Fr may also be utilized. Inanother configuration, the lead body 12 may have a flat, ribbon, orpaddle shape with solid, woven filament, or metal mesh structure, alongat least a portion of the length of the lead body 12. In such anexample, the width across the lead body 12 may be between 1-3.5 mm.Other lead body designs may be used without departing from the scope ofthis application.

The lead body 12 of lead 10 may be formed from a non-conductivematerial, including silicone, polyurethane, fluoropolymers, mixturesthereof, and other appropriate materials, and shaped to form one or morelumens (not shown), however, the techniques are not limited to suchconstructions. The distal portion 16 may be fabricated to be biased in adesired configuration, or alternatively, may be manipulated by the userinto the desired configuration. For example, the distal portion 16 maybe composed of a malleable material such that the user can manipulatethe distal portion into a desired configuration where it remains untilmanipulated to a different configuration.

The lead body 12 may include a proximal end 14 and a distal portion 16which include an electrical stimulation therapy portion 18 configured todeliver electrical energy to the heart or sense electrical energy of theheart. The distal portion 16 may be anchored to a desired positionedwithin the patient, for example, substernally or subcutaneously by, forexample, suturing the distal portion 16 to the patient's musculature,tissue, or bone at the xiphoid process entry site. Alternatively, thedistal portion 16 may be anchored to the patient or through the use ofrigid tines, prongs, barbs, clips, screws, and/or other projectingelements or flanges, disks, pliant tines, flaps, porous structures suchas a mesh-like element and metallic or non-metallic scafolds thatfacilitate tissue growth for engagement, bio-adhesive surfaces, and/orany other non-piercing elements.

The lead body 12 may define a substantially linear portion 20 as itcurves or bends near the xiphoid process and extends superiorly. Asshown in FIGS. 1-3 , at least a part of the distal portion 16 may definean undulating configuration 22 distal to the substantially linearportion 20. In particular, the distal portion 16 may define anundulating pattern, e.g., (zig-zag, meandering, sinusoidal, serpentine,or other pattern) as it extends toward the distal end of the distalportion 16. In other configurations, the lead body 12 may not have asubstantially linear portion 20 as it extends superiorily, but insteadthe undulating configuration may begin immediately after the bend.

The undulating configuration 22 may include a plurality of peaks 24along the length of the distal portion 16. In an exemplaryconfiguration, the undulating configuration 22 of lead 10 includes threepeaks 24 a, 24 b, and 24 c. In other configurations, however, theundulating configuration 22 may include any number of peaks 24. Forexample, the number of peaks 24 may be fewer or greater than threedepending on the frequency of the undulation configuration 22. Forexample, a higher frequency undulating configuration 22 may include morepeaks 24 (e.g., as illustrated in the examples illustrated in FIGS. 6-9) while a lower frequency undulating configuration 22 may include fewerpeaks 24 (e.g., as illustrated in the examples of FIGS. 4 and 5 ).

The undulating configuration 22 may further define a peak-to-peakdistance “d,” (shown in FIG. 3 ), which may be variable or constantalong the length of the undulating configuration 22. In theconfiguration illustrated in FIGS. 1-3 , the undulating configuration 22defines a substantially sinusoidal configuration, with a constantpeak-to-peak distance “d” of approximately 2.0-5.0 cm. The undulatingconfiguration 22 may also define a peak-to-peak width “w,” (shown inFIG. 3 ), which may also be variable or constant along the length of theundulating configuration 22. In the configuration illustrated in FIGS.1-3 , the undulating configuration 22 defines a substantially sinusoidalshape, with a constant peak-to-peak width “w” of approximately 0.5-2.0cm. However, in other instances, the undulating configuration 22 maydefine other shapes and/or patterns, e.g., S-shapes, wave shapes, or thelike.

The distal portion 16 includes a defibrillation electrode 26 configuredto deliver a cardioversion/defibrillation shock to the patient's heart.The defibrillation electrode 26 may include a plurality of sections orsegments 28 spaced a distance apart from each other along the length ofthe distal portion 16. The defibrillation electrode segments 28 may be adisposed around or within the lead body 12 of the distal portion 16, oralternatively, may be embedded within the wall of the lead body 12. Inone configuration, the defibrillation electrode segments 28 may be acoil electrode formed by a conductor. The conductor may be formed of oneor more conductive polymers, ceramics, metal-polymer composites,semiconductors, metals or metal alloys, including but not limited to,one of or a combination of the platinum, tantalum, titanium, niobium,zirconium, ruthenium, indium, gold, palladium, iron, zinc, silver,nickel, aluminum, molybdenum, stainless steel, MP35N, carbon, copper,polyaniline, polypyrrole and other polymers. In another configuration,each of the defibrillation electrodes segments 28 may be a flat ribbonelectrode, a paddle electrode, a braided or woven electrode, a meshelectrode, a directional electrode, a patch electrode or another type ofelectrode configured to deliver a cardioversion/defibrillation shock tothe patient's heart.

In the example illustrated in FIGS. 1-3 , defibrillation electrode 26includes two sections or segments 28 a and 28 b, collectively 28. Thedefibrillation electrode segments 28 extend along a substantial part ofundulating portion 22, e.g., along at least 80% of undulating portion22. The defibrillation electrode segments 28 may extend along more orless than 80% of the undulating configuration 22. As another example,the defibrillation electrode segments 28 may extend along at least 90%of the undulating configuration 22. The defibrillation electrode segment28 a extends along a substantial portion of undulation from the proximalend of undulating portion 22 to peak 24 b (e.g., along a substantialportion of the first “wave” associated with peak 24 a) and thedefibrillation electrode segment 28 b extends along a substantialportion of undulation from peak 24 b to distal end of undulating portion22 (e.g., along a substantial portion of the second “wave” associatedwith peak 24 c). In the example illustrated in FIGS. 1-3 , the only partof undulating portion 22 that defibrillation electrode 26 is notdisposed on is the gap 30 on peak 24 b where electrode 32 b is disposed.

In one configuration, the defibrillation electrode segments 28 arespaced approximately 0.25-4.5 cm, and in some instances between 1-3 cmapart from each other. In another configuration, the defibrillationelectrode segments 28 are spaced approximately 0.25-1.5 cm apart fromeach other. In a further configuration, the defibrillation electrodesegments 28 are spaced approximately 1.5-4.5 cm apart from each other.In the configuration shown in FIGS. 1-3 , the defibrillation electrodesegments 28 span a substantial part of the distal portion 16. Each ofthe defibrillation electrode segments 28 may be between approximately1-10 cm in length and, more preferably, between 2-6 cm in length and,even more preferably, between 3-5 cm in length. However, lengths ofgreater than 10 cm and less than 1 cm may be utilized without departingfrom the scope of this disclosure. A total length of defibrillationelectrode 26 (e.g., length of the two segments 28 combined) may varydepending on a number of variables. The defibrillation electrode 26 may,in one example, have a total length of between approximately 5-10 cm.However, the defibrillation electrode segments 24 may have a totallength less than 5 cm and greater than 10 cm in other embodiments. Insome instances, defibrillation segments 28 may be approximately the samelength or, alternatively, different lengths.

The defibrillation electrode segments 28 may be electrically connectedto one or more conductors, which may be disposed in the body wall of thelead body 12 or may alternatively be disposed in one or more insulatedlumens (not shown) defined by the lead body 12. In an exemplaryconfiguration, each of the defibrillation electrode segments 28 isconnected to a common conductor such that a voltage may be appliedsimultaneously to all the defibrillation electrode segments 28 todeliver a defibrillation shock to a patient's heart. In otherconfigurations, the defibrillation electrode segments 28 may be attachedto separate conductors such that each defibrillation electrode segment28 may apply a voltage independent of the other defibrillation electrodesegments 28. In this case, ICD 9 or lead 10 may include one or moreswitches or other mechanisms to electrically connect the defibrillationelectrode segments together to function as a common polarity electrodesuch that a voltage may be applied simultaneously to all thedefibrillation electrode segments 28 in addition to being able toindependently apply a voltage.

The distal portion 16 may define one or more gaps 30 between adjacentdefibrillation segments 28. The gaps 30 may define any length. Ininstances in which more than two defibrillation segments 28 exist, eachgap 30 may define the same or substantially the same length as everyother gap 30 or may define a different length than other gap 30 in thedistal portion. In the example of FIG. 3 , a single gap 30 existsbetween defibrillation electrode segments 28. One or more electrodes 32may be disposed within the respective gap 30. In the configuration shownin FIG. 1 , a single electrode 32 b is disposed within the gap 30.However, in other examples, more than one electrode 32 may exist withinthe gap 30 (e.g., as illustrated in the example of FIGS. 4 and 8 ). Inthe configuration shown in FIG. 1 , another electrode 32 a is locatedproximal to defibrillation electrode segment 28 a. In otherconfigurations, additional electrodes 32 may be disposed along thedistal portion 16 of lead 10, e.g., distal to defibrillation electrodesegment 28 b and/or proximal to electrode segment 28 a.

In one example, the distance between the closest defibrillationelectrode segment 28 and electrodes 32 is greater than or equal to 2 mmand less than or equal to 1.5 cm. In another example, electrodes 32 maybe spaced apart from the closest one of defibrillation electrodesegments 28 by greater than or equal to 5 mm and less than or equal to 1cm. In a further example, electrodes 32 may be spaced apart from theclosest one of defibrillation electrode segments 28 by greater than orequal to 6 mm and less than or equal to 8 mm.

The electrodes 32 a and 32 b may be configured to deliver low-voltageelectrical pulses to the heart or may sense a cardiac electricalactivity, e.g., depolarization and repolarization of the heart. As such,electrodes 32 may be referred to herein as pace/sense electrodes 32. Inone configuration, the electrodes 32 are ring electrodes. However, inother configurations the electrodes 32 may be any of a number ofdifferent types of electrodes, including ring electrodes, short coilelectrodes, paddle electrodes, hemispherical electrodes, directionalelectrodes, or the like. The electrodes 32 may be the same or differenttypes of electrodes. The electrodes 32 may be electrically isolated froman adjacent defibrillation segment 28 by including an electricallyinsulating layer of material between the electrodes 32 and the adjacentdefibrillation segments 28. Each electrode 32 may have its own separateconductor such that a voltage may be applied to each electrodeindependently from another electrode 32 in the distal portion 16. Inother configurations, each electrode 32 may be coupled to a commonconductor such that each electrode 32 may apply a voltagesimultaneously.

In the configurations shown in FIGS. 1-3 , each electrode 32 issubstantially aligned along a major longitudinal axis (“x”). In oneexample, the major longitudinal axis is defined by a portion of theelongate body 12, e.g., the substantially linear portion 20. In anotherexample, the major longitudinal axis is defined relative to the body ofthe patient, e.g., along the anterior median line (or midsternal line),one of the sternal lines (or lateral sternal lines), left parasternalline, or other line. The electrodes 32 a and 32 b may be disposed alongthe undulating configuration 22 such that each electrode 32 a and 32 bis substantially aligned or otherwise disposed along the majorlongitudinal axis “x.” In one configuration, the midpoint of eachelectrode 32 a and 32 b is along the major longitudinal axis “x,” suchthat each electrode 32 a and 32 b is at least disposed at substantiallythe same horizontal position when the distal portion is implanted withinthe patient. In other configurations, the electrodes 32 may be disposedat any longitudinal or horizontal position along the distal portion 16disposed between, proximal to, or distal to the defibrillation electrodesegments 28, as described in other embodiments herein. In the exampleillustrated in FIGS. 1-3 , the electrodes 32 are disposed along theundulating configuration 22 at locations that will be closer to theheart of the patient than defibrillation electrode segments 28 (e.g., atpeak 24 b that is toward the left side of the sternum). As illustratedin FIG. 1A, for example, the electrodes 32 are substantially alignedwith one another along the left sternal line. The defibrillationelectrode segments 28 are disposed along the peaks 24 a and 24 c thatextend toward a right side of the sternum away from the heart. Thisconfiguration places the pace/sense electrodes 32 at locations closer tothe heart and thereby lower pacing thresholds and better sense cardiacactivity of the heart.

As illustrated in longitudinal side view of distal portion 16 of FIG.3B, the pace/sense electrodes 32 and the defibrillation electrodesegments 28 may further be disposed in a common plane when the distalportion 16 is implanted extracardiovasculalry. In particular, theundulating configuration 22 is substantially disposed in a plane definedby the longitudinal axis “x” and a horizontal axis (“y”), referred toherein as the horizontal plane (e.g., the x-y plane). In the exampleillustrated in FIG. 3B, each defibrillation electrode segment 28 andeach electrode 32 is at least partially disposed in the horizontalplane. Optionally, in other configurations, the undulating configuration22 may not be substantially disposed in the horizontal plane. Instead,the electrical stimulation therapy portion 18 may be curved such thatone or more the defibrillation electrode segments 28 or pace/senseelectrodes 32 may be pressed inward toward the heart. For example, theelectrical stimulation therapy portion 18 may define a concavity or acurvature to place the one or more of the defibrillation electrodesegments 28 or the pace/sense electrodes 32 close to the heart. In suchcase, the undulating portion 22 may be viewed as being a 3-dimensionalserpentine shape in which some of the peaks or portions of the peaks 24extend in the z-direction, perpendicular to the horizontal plane andtoward the heart.

The proximal end 14 of the lead body 12 may include one or moreconnectors 34 to electrically couple the lead 10 to the implantablecardioverter-defibrillator (ICD) 9 subcutaneously implanted within thepatient, for example, under the left armpit of the patient. The ICD 9may include a housing 38 that forms a hermetic seal which protects thecomponents of ICD 9. The housing 38 of ICD 9 may be formed of aconductive material, such as titanium or titanium alloy, which mayfunction as a housing electrode for a particular therapy vector asillustrated by the arrows in FIG. 1 between the housing 38 and thedistal portion 16. The ICD 36 may also include a connector assembly thatincludes electrical feedthroughs through which electrical connectionsare made between the one or more connectors 34 of lead 10 and theelectronic components included within the housing 38. The housing 38 mayhouse one or more processors, memories, transmitters, receivers,sensors, sensing circuitry, therapy circuitry, power sources (capacitorsand batteries) and/or other appropriate components. The components ofICD 9 may generate and deliver electrical stimulation therapy such asanti-tachycardia pacing, cardioversion or defibrillation shocks,post-shock pacing, bradycardia pacing, or other electrical stimulation.

The particular configuration of the undulating configuration 22 and theinclusion of the electrodes 32 between defibrillation electrode segments28 provides a number of therapy vectors for the delivery of electricalstimulation therapy to the heart. For example, as shown in FIGS. 1-3 ,at least a portion of the defibrillation electrode 26 and one of theelectrodes 32 may be disposed over the right ventricle, or any chamberof the heart, such that pacing pulses and defibrillation shocks may bedelivered to the heart from the therapy portion 18. The housing 38 maybe charged with or function as a polarity different than the polarity ofthe one or more defibrillation electrode segments 28 and/or electrodes32 such that electrical energy may be delivered between the housing 38and the defibrillation electrode segment(s) 28 and/or electrode(s) 32 tothe heart. Each defibrillation electrode segment 28 may have the samepolarity as every other defibrillation electrode segment 28 when avoltage is applied to it such that a defibrillation shock may bedelivered from the entirety of the defibrillation electrode 26. Inembodiments in which defibrillation electrode segments 28 areelectrically connected to a common conductor within lead body 12, thisis the only configuration of defibrillation electrode segments 28.However, in other embodiments, defibrillation electrode segments 28 maybe coupled to separate conductors within lead body 12 and may thereforeeach have different polarities such that electrical energy may flowbetween defibrillation electrode segments 28 (or between one ofdefibrillation electrode segments 28 and one or pace/sense electrodes 32or the housing electrode) to provide pacing therapy and/or to sensecardiac depolarizations. In this case, the defibrillation electrodesegments 28 may still be electrically coupled together (e.g., via one ormore switches within ICD 9) to have the same polarity to deliver adefibrillation shock from the entirety of the defibrillation electrode26.

Additionally, each electrode 32 may be configured to conduct electricalpulses directly to the heart, or sense a cardiac depolarization betweenadjacent defibrillation electrode segments 28, whether disposed on thesame defibrillation electrode segment 28 or on other defibrillationelectrode segment 28, and/or between proximate electrodes 32. Forexample, the therapy vector lines shown in FIG. 3 illustrate the flow ofelectrical energy between the electrodes 32 a and 32 b and adjacentdefibrillation electrode segments 28. The therapy vector linesillustrate potential vectors that can be generated to target specificareas of the heart for electrical stimulation therapy or to targetdifferent areas of the heart so as to be able to select a pacing and/orsensing vector with best performance (e.g., lowest pacing capturethresholds). Additionally electrodes 32 may conduct electrical pulsesbetween one another, e.g., between one of electrodes 32 and an inferiorand superior electrode 32, between one of electrodes 32 and the housingelectrode, or between a plurality of electrodes 32 (at the samepolarity) and the housing electrode at the opposite polarity. As such,each electrode 32 may have the same polarity as every other electrode 32or alternatively, may have different polarities such that differenttherapy vectors can be utilized to deliver pacing pulses to the heart.

FIG. 4 is a schematic diagram illustrating another example lead 40constructed in accordance with the principles of the presentapplication. Lead 40 can include one or more of the structure and/orfunctionality of lead 10 of FIGS. 1-3 (and vice versa), including theelectrode and lead body dimensions, spacings, materials, shapes,orientations, electrical conductor configurations, and the like.Repetitive description of like numbered elements described in otherembodiments is omitted for sake of brevity.

Lead 40 includes an undulating portion 42. Undulating portion 42 issubstantially similar to undulating portion 22 of lead 10, butundulating portion 42 includes only two peaks 24. However, undulatingportion 42 may define a peak-to-peak distance “d” and peak-to-peak width“w” with similar dimensions described above with respect to FIGS. 1-3 .

Lead 40 includes a defibrillation electrode 26 formed from twodefibrillation electrode segments 28 a and 28 b. The defibrillationelectrode segments 28 extend along a substantial part of undulatingportion 42, e.g., along at least 80% of undulating portion 42. Thedefibrillation electrode segment 28 a extends along a substantialportion of undulation from the proximal end of undulating portion 42,except for the part of undulating portion 42 that includes the gap 30where electrode 32 b is disposed. In the example illustrated in FIG. 4 ,the gap 30 and electrode 32 b are located along the part of undulatingportion 42 that transitions from peak 24 a to peak 24 b, instead of at apeak as was the case in lead 10 of FIGS. 1-3 .

Lead 40 also includes two pace/sense electrodes 32 a and 32 b. Theelectrodes 32 a and 32 b are disposed along the undulating configuration42 such that each electrode 32 a and 32 b is substantially aligned orotherwise disposed along the major longitudinal axis “x.” Unlike in lead10 of FIGS. 1-3 , however, the orientation of electrodes 32 a and 32 bare different even though they are substantially disposed atsubstantially the same horizontal position when the distal portion isimplanted within the patient. Moreover, electrodes 32 are disposed alongthe undulating configuration 42 at locations such that the electrodes 32will be substantially aligned with one another along the anterior medianline instead of the left sternal line. In this case, the defibrillationelectrode segment 28 a is disposed along the peak 24 a and will extendtoward the left side of the sternum when implanted and defibrillationelectrode segment 28 b is disposed along the peak 24 b and will extendtoward the right side of the sternum when implanted.

Defibrillation electrode segments 28 and pace/sense electrodes 32 mayinclude the structure and functionality described above with respect toFIGS. 1-3 , including but not limited to the spacing between segments 28and electrodes 32, the size of segments 28 and 32, electrode and leadbody dimensions, spacings, materials, shapes, and the like.Additionally, as described above with respect to FIGS. 1-3 , in someconfigurations defibrillation electrode segments 28 may each beconnected to a common conductor such that a voltage may be appliedsimultaneously to all the defibrillation electrode segments 28 (and theyfunction as a single polarity) to deliver a defibrillation shock to apatient's heart. In other configurations, the defibrillation electrodesegments 28 may be attached to separate conductors such that eachdefibrillation electrode segment 28 may apply a voltage independent ofthe other defibrillation electrode segments 28. In this case, ICD 9 orlead 40 may include one or more switches or other mechanisms toelectrically connect the defibrillation electrode segments together tofunction as a common polarity electrode such that a voltage may beapplied simultaneously to all the defibrillation electrode segments 28in addition to being able to independently apply a voltage.

FIG. 5 is a schematic diagram illustrating another example lead 50constructed in accordance with the principles of the presentapplication. Lead 50 can include one or more of the structure and/orfunctionality of lead 10 of FIGS. 1-3 (and vice versa) or lead 40 ofFIG. 4 , including the electrode and lead body dimensions, spacings,materials, shapes, orientations, electrical conductor configurations,and the like. Repetitive description of like numbered elements describedin other embodiments is omitted for sake of brevity.

Lead 50 includes an undulating portion 52. Undulating portion 52includes two peaks 24, similar to undulating portion 42 of lead 40, butundulating portion 52 includes a longer peak-to-peak width “w.” Lead 50also includes three pace/sense electrodes 32 with two of them beingdisposed between defibrillation electrode segments 28. Unlike theexample leads illustrated in FIGS. 1-4 , at least one of the pace/senseelectrodes 32 is not substantially aligned or otherwise disposed alongthe major longitudinal axis “x.”

FIG. 6 is a schematic diagram illustrating another example lead 60constructed in accordance with the principles of the presentapplication. Lead 60 can include one or more of the structure and/orfunctionality of lead 10 of FIGS. 1-3 , lead 40 of FIG. 4 , and/or lead50 of FIG. 5 (and vice versa), including the electrode and lead bodydimensions, spacings, materials, shapes, orientations, electricalconductor configurations, and the like. Repetitive description of likenumbered elements described in other embodiments is omitted for sake ofbrevity.

Lead 60 includes an undulating portion 62. Undulating portion 62 issubstantially similar to undulating portion 22 of lead 10, butundulating portion 62 includes seven peaks 24 a-g instead of threepeaks. Undulating portion 62 defines a peak-to-peak distance “d” withsimilar dimensions described above with respect to FIGS. 1-3 , but thepeak-to-peak width “w” may be smaller than the peak-to-peak widths ofundulating portions 22, 42, or 52 due to the increased number of peaks24.

The defibrillation electrode also includes more defibrillation electrodesegments 28 than the leads 10, 40 and 50. The defibrillation electrodesegments 28 extend along a substantial part of undulating portion 62,e.g., along at least 80% of undulating portion 62. The defibrillationelectrode segments 28 extend along a substantial portion of undulationfrom the proximal end of undulating portion 62, except for the part ofundulating portion 62 that includes the gaps 30 where electrodes 32 aredisposed. In the example illustrated in FIG. 6 , the gaps 30 andelectrodes 32 b are located along the part of undulating portions 62that transition from a peak 24 to adjacent peak 24 (at every othertransition), instead of at a peak as was the case in lead 10 of FIGS.1-3 .

Lead 60 also includes three pace/sense electrodes 32 a-32 c. Theelectrodes 32 are disposed along the undulating configuration 62 suchthat each electrode 32 is substantially aligned or otherwise disposedalong the major longitudinal axis “x.” Unlike in lead 10, 40 and 50 ofFIGS. 1-5 , however, all electrodes 32 are located between adjacentdefibrillation electrode segments 28. In other instances, the lead 60may also include one or more electrodes 32 proximal to the most proximaldefibrillation electrode segment 28 or distal to the most distaldefibrillation electrode segment 28. Electrodes 32 are disposed alongthe undulating configuration 62 at locations such that the electrodes 32will be substantially aligned with one another along the anterior medianline.

Defibrillation electrode segments 28 and pace/sense electrodes 32 mayinclude the structure and functionality described above with respect toFIGS. 1-3 , including but not limited to the spacing between segments 28and electrodes 32, the size of segments 28 and 32, electrode and leadbody dimensions, spacings, materials, shapes, and the like.Additionally, as described above with respect to FIGS. 1-3 , in someconfigurations defibrillation electrode segments 28 may each beconnected to a common conductor such that a voltage may be appliedsimultaneously to all the defibrillation electrode segments 28 (and theyfunction as a single polarity) to deliver a defibrillation shock to apatient's heart. In other configurations, the defibrillation electrodesegments 28 may be attached to separate conductors such that eachdefibrillation electrode segment 28 may apply a voltage independent ofthe other defibrillation electrode segments 28. In this case, ICD 9 orlead 60 may include one or more switches or other mechanisms toelectrically connect the defibrillation electrode segments together tofunction as a common polarity electrode such that a voltage may beapplied simultaneously to all the defibrillation electrode segments 28in addition to being able to independently apply a voltage.

FIG. 7 is a schematic diagram illustrating another example lead 70constructed in accordance with the principles of the presentapplication. Lead 70 can include one or more of the structure and/orfunctionality of lead 10 of FIGS. 1-3 , lead 40 of FIG. 4 , lead 50 ofFIG. 5 and/or lead 60 of FIG. 6 (and vice versa), including theelectrode and lead body dimensions, spacings, materials, shapes,orientations, electrical conductor configurations, and the like.Repetitive description of like numbered elements described in otherembodiments is omitted for sake of brevity.

Lead 70 includes an undulating portion 72 that is substantially similarto undulating portion 62 of lead 60 of FIG. 6 except that the electrode32 may be sized to span the distance between two peaks 24 in theundulating configuration 72. In this configuration, the electrodes 32may be configured to sense a cardiac depolarization between an adjacentdefibrillation electrode segment 28. Moreover, the electrodes 32 areconfigured to deliver pacing pulses to the heart by conductiveelectrical energy between the electrodes 32 and an adjacentdefibrillation electrode segment 28. In such a configuration, thetherapy vectors between a respective electrode 32 and an adjacentdefibrillation electrode segment 28 may define a substantially rhomboidor diamond configuration to provide for a particular therapy vector.Electrodes 32 may also deliver electrical energy between respective onesof electrodes 32. Repetitive description of like numbered elementsdescribed in other embodiments is omitted for the sake of brevity.

FIG. 8 is a schematic diagram illustrating another example lead 80constructed in accordance with the principles of the presentapplication. Lead 80 can include one or more of the structure and/orfunctionality of lead 10 of FIGS. 1-3 , lead 40 of FIG. 4 , lead 50 ofFIG. 5 lead 60 of FIG. 6 , and/or lead 70 of FIG. 7 (and vice versa),including the electrode and lead body dimensions, spacings, materials,shapes, orientations, electrical conductor configurations, and the like.Repetitive description of like numbered elements described in otherembodiments is omitted for sake of brevity.

Lead 80 includes an undulating portion 82 that may conform substantiallyto undulating portion 62 of lead 60 of FIG. 6 and/or undulating portion72 of lead 70 of FIG. 7 except that two or more electrodes 32 may spanthe distance between two peaks 24 in the undulating configuration 62.The electrodes 32 may be disposed in a single gap 30 between adjacentdefibrillation electrode segments 28 or each electrode 32 may bedisposed in a two gaps 30 and each gap 30 is separated by anelectrically insulating section of the lead body 12. In theconfiguration shown in FIG. 8 , the electrodes 32 may be configured tosense a cardiac depolarization between each other or an adjacentdefibrillation electrode segment 28, depending on the polarity of eachelectrode 32. Moreover, the electrodes 32 are configured to deliverpacing pulses to the heart with conductive electrical energy between theelectrodes 32 and an adjacent defibrillation electrode segment 28 orbetween two of the electrodes 32. For example, therapy vectors are shownin FIG. 8 for a configuration in which, for example, electrodes 32 a and32 a′ have the same polarity and the opposite polarity of an adjacentdefibrillation electrode segment 28 to provide for a particular therapyvector. However, electrodes 32 a and 32 a′, and likewise 32 b and 32 b′and 32 c, and 32 c′ may be coupled to the same or different conductorssuch that the polarities between each electrode 32 may be the same ordifferent depending on the application. Between each electrode 32 a and32 a′, for example, may be a portion of the lead body 12 that iselectrically insulating. Moreover, the gaps 30 may be sized to optimizeparticular electrical stimulation therapies. For example, the gap 30size may range from approximately 8 mm-15 mm for between a pair ofelectrodes 32 configured to pace and/or sense a cardiac depolarization.Additionally, the size of the gaps 30 between an electrode 32 and adefibrillation electrode segment 28 may be approximately 3-10 mm inlength or any of the lengths described above with respect to FIGS. 1-3 .Repetitive description of like numbered elements described in otherembodiments is omitted for sake of brevity.

FIG. 9 is a schematic diagram illustrating another example lead 90constructed in accordance with the principles of the presentapplication. Lead 90 can include one or more of the structure and/orfunctionality of lead 10 of FIGS. 1-3 , lead 40 of FIG. 4 , lead 50 ofFIG. 5 and/or lead 60 of FIG. 6 , lead 70 of FIG. 7 , and/or lead 80 ofFIG. 8 (and vice versa), including the electrode and lead bodydimensions, spacings, materials, shapes, orientations, electricalconductor configurations, and the like. Repetitive description of likenumbered elements described in other embodiments is omitted for sake ofbrevity.

Lead 90 includes an undulating portion 92 that may conform substantiallyto undulating portion 62 of lead 60 of FIG. 6 except that electrodes 32may be directional electrodes positioned to provide a therapy vectoraimed at the heart and not skeletal muscle, such that only a portion ofthe lead body in which the electrodes 32 are disposed contain theelectrode 32 and another portion includes the insulating portion of thelead body. The electrodes 32 would be arranged such that the electrodesare disposed on the posterior side of the lead (e.g., facing the heart)when implanted within the patient. In this configuration, the electrodes32 may be configured to sense a cardiac depolarization between anadjacent defibrillation electrode segment 28, between two of electrodes32, or between electrode(s) 32 and housing electrode. Moreover, theelectrodes 32 are configured to deliver pacing pulses to the heart byconductive electrical energy between an adjacent defibrillationelectrode segment 28, between two of electrodes 32, or betweenelectrode(s) 32 and housing electrode. For example, therapy vectors areshown in FIG. 6 for a configuration in which each electrode 32 a, 32 b,and 32 c are disposed on the superior portion of a lead body 62 section.In other configurations, for example, electrodes 32 a and 32 c may befacing electrode 32 b to provide for particular therapy vectors. Thearrangement of electrodes 32 a, 32 b, and 32 c may be such thatelectrical energy is directed toward the heart and not toward skeletalmuscle or non-cardiac tissue to maximize the effectiveness of pacingpulses delivered to the heart. Repetitive description of like numberedelements described in other embodiments is omitted for sake of brevity.

FIG. 10 is a functional block diagram of an example configuration ofelectronic components of an example ICD 9. ICD 9 includes a controlmodule 100, sensing module 102, therapy module 104, communication module108, and memory 110. The electronic components may receive power from apower source 106, which may be a rechargeable or non-rechargeablebattery. In other embodiments, ICD 9 may include more or fewerelectronic components. The described modules may be implemented togetheron a common hardware component or separately as discrete butinteroperable hardware or software components. Depiction of differentfeatures as modules is intended to highlight different functionalaspects and does not necessarily imply that such modules must berealized by separate hardware or software components. Rather,functionality associated with one or more modules may be performed byseparate hardware or software components, or integrated within common orseparate hardware or software components. FIG. 10 will be described inthe context of ICD 9 being coupled to lead 10 for exemplary purposesonly. However, ICD 9 may be coupled to other leads, such as lead 40, 50,60, 70, 80 or 90 described herein, and thus other electrodes.

Sensing module 102 is electrically coupled to some or all of electrodes26 (or separately to segments 28 a and/or 28 b) and 32 via theconductors of lead 10 and one or more electrical feedthroughs, or to thehousing electrode via conductors internal to the housing of ICD 9.Sensing module 102 is configured to obtain signals sensed via one ormore combinations of electrodes 26 (or separately to segments 28 aand/or 28 b) and 32 and the housing electrode of ICD 9 and process theobtained signals.

The components of sensing module 102 may be analog components, digitalcomponents or a combination thereof. Sensing module 102 may, forexample, include one or more sense amplifiers, filters, rectifiers,threshold detectors, analog-to-digital converters (ADCs) or the like.Sensing module 102 may convert the sensed signals to digital form andprovide the digital signals to control module 100 for processing oranalysis. For example, sensing module 102 may amplify signals from thesensing electrodes and convert the amplified signals to multi-bitdigital signals by an ADC. Sensing module 102 may also compare processedsignals to a threshold to detect the existence of atrial or ventriculardepolarizations (e.g., P- or R-waves) and indicate the existence of theatrial depolarization (e.g., P-waves) or ventricular depolarizations(e.g., R-waves) to control module 100.

Control module 100 may process the signals from sensing module 102 tomonitor electrical activity of the heart of the patient. Control module100 may store signals obtained by sensing module 102 as well as anygenerated EGM waveforms, marker channel data or other data derived basedon the sensed signals in memory 110. Control module 100 may analyze theEGM waveforms and/or marker channel data to detect cardiac events (e.g.,tachycardia). In response to detecting the cardiac event, control module100 may control therapy module 104 to deliver the desired therapy totreat the cardiac event, e.g., defibrillation shock, cardioversionshock, ATP, post-shock pacing, or bradycardia pacing.

Therapy module 104 is configured to generate and deliver electricalstimulation therapy to the heart. Therapy module 104 may include one ormore pulse generators, capacitors, and/or other components capable ofgenerating and/or storing energy to deliver as pacing therapy,defibrillation therapy, cardioversion therapy, cardiac resynchronizationtherapy, other therapy or a combination of therapies. In some instances,therapy module 104 may include a first set of components configured toprovide pacing therapy and a second set of components configured toprovide defibrillation therapy. In other instances, therapy module 104may utilize the same set of components to provide both pacing anddefibrillation therapy. In still other instances, therapy module 104 mayshare some of the defibrillation and pacing therapy components whileusing other components solely for defibrillation or pacing.

Control module 100 may control therapy module 104 to deliver thegenerated therapy to the heart via one or more combinations ofelectrodes 26 (or separately to segments 28 a and/or 28 b) and 32 oflead 10 and the housing electrode of ICD 9 according to one or moretherapy programs, which may be stored in memory 110. In instances inwhich control module 100 is coupled to a different lead, e.g., lead 40,50, 60, 70, 80, or 90, other electrodes may be utilized. Control module100 controls therapy module 104 to generate electrical stimulationtherapy with the amplitudes, pulse widths, timing, frequencies,electrode combinations or electrode configurations specified by aselected therapy program.

Therapy module 104 may include a switch module to select which of theavailable electrodes are used to deliver the therapy. The switch modulemay include a switch array, switch matrix, multiplexer, or any othertype of switching device suitable to selectively couple electrodes totherapy module 104. Control module 100 may select the electrodes tofunction as therapy electrodes, or the therapy vector, via the switchmodule within therapy module 104. In instances in which defibrillationsegments 28 a and 28 b are each coupled to separate conductors, controlmodule 100 may be configured to selectively couple therapy module 104 toeither one of segments 28 a and 28 b individually or couple to both ofthe segments 28 a and 28 b concurrently. In some instances, the sameswitch module may be used by both therapy module 104 and sensing module102. In other instances, each of sensing module 102 and therapy module104 may have separate switch modules.

In the case of pacing therapy being provided, e.g., ATP, post-shockpacing, and/or bradycardia pacing provided via electrodes 32 and/ordefibrillation electrode segments 28 a and 28 b of lead 10. In oneexample, therapy module 104 may deliver pacing (e.g., ATP or post-shockpacing) using an electrode vector that includes one or bothdefibrillation electrode segments 28 a and 28 b. The electrode vectorused for pacing may be segment 28 a as an anode (or cathode) and one ofelectrodes 28 b, 32 or the housing of ICD 9 as the cathode (or anode) orsegment 28 b as an anode (or cathode) and one of electrodes 28 b, 32 orthe housing of ICD 9 as the cathode (or anode). If necessary, therapymodule 104 may generate and deliver a cardioversion/defibrillation shock(or shocks) using one or both of electrode segments 28 concurrently as acathode and the housing electrode of ICD 9 as an anode.

Control module 100 controls therapy module 104 to generate and deliverpacing pulses with any of a number of shapes, amplitudes, pulse widths,or other characteristic to capture the heart. For example, the pacingpulses may be monophasic, biphasic, or multi-phasic (e.g., more than twophases). The pacing thresholds of the heart when delivering pacingpulses from the substernal space, e.g., from electrodes 32 and/orelectrode segments 28 substantially within anterior mediastinum 36, maydepend upon a number of factors, including location, type, size,orientation, and/or spacing of electrodes 32 and/or electrode segments28, location of ICD 9 relative to electrodes 32 and/or electrodesegments 28, physical abnormalities of the heart (e.g., pericardialadhesions or myocardial infarctions), or other factor(s).

The increased distance from electrodes 32 and/or electrode segments 28of lead 10 to the heart tissue may result in the heart having increasedpacing thresholds compared to transvenous pacing thresholds. To thisend, therapy module 104 may be configured to generate and deliver pacingpulses having larger amplitudes and/or pulse widths than conventionallyrequired to obtain capture via leads implanted within the heart (e.g.,transvenous leads) or leads attached directly to the heart. In oneexample, therapy module 104 may generate and deliver pacing pulseshaving amplitudes of less than or equal to 8 volts and pulse widthsbetween 0.5-3.0 milliseconds and, in some instances up to 4milliseconds. In another example, therapy module 104 may generate anddeliver pacing pulses having amplitudes of between 5 and 10 volts andpulse widths between approximately 3.0 milliseconds and 10.0milliseconds. In another example, therapy module 104 may generate anddeliver pacing pulses having pulse widths between approximately 2.0milliseconds and 8.0 milliseconds. In a further example, therapy module104 may generate and deliver pacing pulses having pulse widths betweenapproximately 0.5 milliseconds and 20.0 milliseconds. In anotherexample, therapy module 104 may generate and deliver pacing pulseshaving pulse widths between approximately 1.5 milliseconds and 20.0milliseconds.

Pacing pulses having longer pulse durations than conventionaltransvenous pacing pulses may result in lower energy consumption. Assuch, therapy module 104 may be configured to generate and deliverpacing pulses having pulse widths or durations of greater than two (2)milliseconds. In another example, therapy module 104 may be configuredto generate and deliver pacing pulses having pulse widths or durationsof between greater than two (2) milliseconds and less than or equal tothree (3) milliseconds. In another example, therapy module 104 may beconfigured to generate and deliver pacing pulses having pulse widths ordurations of greater than or equal to three (3) milliseconds. In anotherexample, therapy module 104 may be configured to generate and deliverpacing pulses having pulse widths or durations of greater than or equalto four (4) milliseconds. In another example, therapy module 104 may beconfigured to generate and deliver pacing pulses having pulse widths ordurations of greater than or equal to five (5) milliseconds. In anotherexample, therapy module 104 may be configured to generate and deliverpacing pulses having pulse widths or durations of greater than or equalto ten (10) milliseconds. In a further example, therapy module 104 maybe configured to generate and deliver pacing pulses having pulse widthsbetween approximately 3-10 milliseconds. In a further example, therapymodule 104 may be configured to generate and deliver pacing pulseshaving pulse widths between approximately 4-10 milliseconds. In afurther example, therapy module 104 may be configured to generate anddeliver pacing pulses having pulse widths or durations of greater thanor equal to fifteen (15) milliseconds. In yet another example, therapymodule 104 may be configured to generate and deliver pacing pulseshaving pulse widths or durations of greater than or equal to twenty (20)milliseconds.

Depending on the pulse widths, ICD 9 may be configured to deliver pacingpulses having pulse amplitudes less than or equal to twenty (20) volts,deliver pacing pulses having pulse amplitudes less than or equal to ten(10) volts, deliver pacing pulses having pulse amplitudes less than orequal to five (5) volts, deliver pacing pulses having pulse amplitudesless than or equal to two and one-half (2.5) volts, deliver pacingpulses having pulse amplitudes less than or equal to one (1) volt. Inother examples, the pacing pulse amplitudes may be greater than 20volts. Typically the lower amplitudes require longer pacing widths asillustrated in the experimental results. Reducing the amplitude ofpacing pulses delivered by ICD 9 reduces the likelihood of extra-cardiacstimulation and lower consumed energy of power source 106.

For pacing therapy provided from the subcutaneous placement of lead 10above the sternum and/or ribcage, pacing amplitudes and pulse widths mayvary, e.g., be increased given the further distances from heart and thevarious anatomical features via which the energy must penetrate.

In the case of cardioversion or defibrillation therapy, e.g.,cardioversion or defibrillation shocks provided by defibrillationelectrode segments 28 (individually or together), control module 100controls therapy module 104 to generate cardioversion or defibrillationshocks having any of a number of waveform properties, includingleading-edge voltage, tilt, delivered energy, pulse phases, and thelike. Therapy module 104 may, for instance, generate monophasic,biphasic or multiphasic waveforms. Additionally, therapy module 104 maygenerate cardioversion or defibrillation waveforms having differentamounts of energy. As with pacing, delivering cardioversion ordefibrillation shocks from the substernal space, e.g., from electrodesegment(s) 28 substantially within anterior mediastinum 36, may reducethe amount of energy that needs to be delivered to defibrillate theheart. When lead 10 is implanted in the substernal space, therapy module104 may generate and deliver cardioversion or defibrillation shockshaving energies of less than 65 J, less than 100 J, between 40-50 J,between 35-100 J, and in some instances less than 35 J. When lead 10 isimplanted subcutaneously, ICD 9 may generate and deliver cardioversionor defibrillation shocks having energies around 65-80 J.

Therapy module 104 may also generate defibrillation waveforms havingdifferent tilts. In the case of a biphasic defibrillation waveform,therapy module 104 may use a 65/65 tilt, a 50/50 tilt, or othercombinations of tilt. The tilts on each phase of the biphasic ormultiphasic waveforms may be the same in some instances, e.g., 65/65tilt. However, in other instances, the tilts on each phase of thebiphasic or multiphasic waveforms may be different, e.g., 65 tilt on thefirst phase and 55 tilt on the second phase. The example deliveredenergies, leading-edge voltages, phases, tilts, and the like areprovided for example purposes only and should not be considered aslimiting of the types of waveform properties that may be utilized toprovide substernal defibrillation via defibrillation electrodesegment(s) 28.

Communication module 108 includes any suitable hardware, firmware,software or any combination thereof for communicating with anotherdevice, such as a clinician programmer, a patient monitoring device, orthe like. For example, communication module 108 may include appropriatemodulation, demodulation, frequency conversion, filtering, and amplifiercomponents for transmission and reception of data with the aid ofantenna 112. Antenna 112 may be located within connector block of ICD 9or within housing ICD 9.

The various modules of ICD 9 may include any one or more processors,controllers, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field-programmable gate arrays (FPGAs), orequivalent discrete or integrated circuitry, including analog circuitry,digital circuitry, or logic circuitry. Memory 110 may includecomputer-readable instructions that, when executed by control module 100or other component of ICD 9, cause one or more components of ICD 9 toperform various functions attributed to those components in thisdisclosure. Memory 110 may include any volatile, non-volatile, magnetic,optical, or electrical media, such as a random access memory (RAM),read-only memory (ROM), non-volatile RAM (NVRAM), static non-volatileRAM (SRAM), electrically-erasable programmable ROM (EEPROM), flashmemory, or any other non-transitory computer-readable storage media.

The leads and systems described herein may be used at least partiallywithin the substernal space, e.g., within anterior mediastinum ofpatient, to provide an extravascular ICD system. An implanter (e.g.,physician) may implant the distal portion of the lead intra-thoracicallyusing any of a number of implant tools, e.g., tunneling rod, sheath, orother tool that can traverse the diagrammatic attachments and form atunnel in the substernal location. For example, the implanter may createan incision near the center of the torso of the patient, e.g., andintroduce the implant tool into the substernal location via theincision. The implant tool is advanced from the incision superior alongthe posterior of the sternum in the substernal location. The distal endof lead 10 (or other lead described herein, e.g., leads 40, 50, 60, 70,80, or 90) is introduced into tunnel via implant tool (e.g., via asheath). As the distal end of lead 10 is advanced through the substernaltunnel, the distal end of lead 10 is relatively straight. The pre-formedor shaped undulating portion 22 is flexible enough to be straightenedout while routing the lead 10 through a sheath or other lumen or channelof the implant tool. Once the distal end of lead 10 is in place, theimplant tool is withdrawn toward the incision and removed from the bodyof the patient while leaving lead 10 in place along the substernal path.As the implant tool is withdrawn, the distal end of lead 10 takes on itspre-formed undulating configuration 22. Thus, as the implant tool iswithdrawn, the undulating configuration 22 pushes electrodes 32 a and 32b toward the left side of sternum compared to electrodes 28 a and 28 b.As mentioned above, the implanter may align the electrodes 32 a and 32 balong the anterior median line (or midsternal line) or the left sternallines (or left lateral sternal line).

It will be appreciated by persons skilled in the art that the presentapplication is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the application, which is limited only by the followingclaims.

The invention claimed is:
 1. An implantable medical electrical leadcomprising: a lead body defining a proximal end and a distal portion,wherein the distal portion of the lead body extends along a longitudinalaxis; a set of defibrillation electrode segments disposed along thedistal portion of the lead body, wherein at least a portion of eachdefibrillation electrode segment of the set of defibrillation electrodesegments is configured to assume a curved shape comprising one or morepeaks displaced from the longitudinal axis; and two or more electrodesdisposed on the lead body, wherein the two or more electrodes areseparate from the set of defibrillation electrode segments, wherein eachelectrode of the two or more electrodes is disposed along thelongitudinal axis of the lead body, wherein a length of eachdefibrillation electrode segment of the set of defibrillation electrodesegments is greater than a length of each electrode of the two or moreelectrodes, and wherein the two or more electrodes are configured toperform at least one of: deliver a pacing pulse to a heart; or sensecardiac electrical activity of the heart.
 2. The lead of claim 1,wherein the distal portion of the lead body is configured to assume anundulating configuration including a plurality of peaks including theone or more peaks of each defibrillation electrode segment of the set ofdefibrillation electrode segments, wherein a first one or more of theplurality of peaks extend in a first direction away from thelongitudinal axis of the lead, wherein a second one or more of theplurality of peaks extend in a second direction away from thelongitudinal axis of the lead, the second direction being an opposite ofthe first direction, and wherein the set of defibrillation electrodesegments are disposed along the first one or more of the plurality ofpeaks and the two or more electrodes are disposed on the second one ormore of the plurality of peaks.
 3. The lead of claim 2, wherein theplurality of peaks of the undulating configuration are within a commonplane.
 4. The lead of claim 2, wherein at least one peak of theplurality of peaks of the undulating configuration is located in a firstplane which is different than a second plane in which at least one otherpeak of the plurality of peaks is located.
 5. The lead of claim 1,wherein the distal portion of the lead body is configured to assume anundulating configuration including a plurality of peaks including theone or more peaks of each defibrillation electrode segment of the set ofdefibrillation electrode segments, wherein the plurality ofdefibrillation electrode segments are disposed to cover at least aportion of the plurality of peaks, and wherein the two or moreelectrodes are disposed to cover a portion of the undulatingconfiguration between consecutive peaks of the plurality of peaks. 6.The lead of claim 1, further comprising a conductor disposed within thelead body, wherein each defibrillation electrode segment of the set ofdefibrillation electrode segments is electrically connected to theconductor.
 7. The lead of claim 6, further comprising a connectordisposed at the proximal end of the lead body, wherein the connector isconfigured to electrically couple with a pulse generator, and whereinthe conductor is coupled to the connector.
 8. The lead of claim 1,wherein the set of defibrillation electrode segments includes a firstdefibrillation electrode segment and a second defibrillation electrodesegment, wherein the lead further comprises: a first conductor disposedwithin the lead body and electrically connected to the firstdefibrillation electrode segment; and a second conductor disposed withinthe lead body and electrically connected to the second defibrillationelectrode segment.
 9. The lead of claim 1, wherein at least oneelectrode of the two or more electrodes is disposed: proximal to eachdefibrillation electrode segment of the set of defibrillation electrodesegments; or distal to the defibrillation electrode segments eachdefibrillation electrode segment of the set of defibrillation segments.10. An implantable cardioverter-defibrillator (ICD) system comprising:an implantable medical electrical lead comprising: a lead body defininga proximal end and a distal portion, wherein the distal portion of thelead body extends along a longitudinal axis; a set of defibrillationelectrode segments disposed along the distal portion of the lead body,wherein at least a portion of each defibrillation electrode segment ofthe set of defibrillation electrode segments is configured to assume acurved shape comprising one or more peaks displaced from thelongitudinal axis; and two or more electrodes disposed on the lead body,wherein the two or more electrodes are separate from the set ofdefibrillation electrode segments, wherein each electrode of the two ormore electrodes is disposed along the longitudinal axis of the leadbody, wherein a length of each defibrillation electrode segment of theset of defibrillation electrode segments is greater than a length ofeach electrode of the two or more electrodes, and wherein the two ormore electrodes are configured to perform at least one of: deliver apacing pulse to a heart; or sense cardiac electrical activity of theheart; and an implantable cardioverter defibrillator (ICD) coupled tothe implantable medical electrical lead, wherein the ICD comprisestherapy circuitry configured to generate and deliver electrical therapy.11. The system of claim 10, wherein the distal portion of the lead bodyis configured to assume an undulating configuration including aplurality of peaks including the one or more peaks of eachdefibrillation electrode segment of the set of defibrillation electrodesegments, wherein a first one or more of the plurality of peaks extendin a first direction away from the longitudinal axis of the lead,wherein a second one or more of the plurality of peaks extend in asecond direction away from major longitudinal axis of the lead, thesecond direction being an opposite of the first direction, and whereinthe set of defibrillation electrode segments are disposed along thefirst one or more of the plurality of peaks and the two or moreelectrodes are disposed on the second one or more of the plurality ofpeaks.
 12. The system of claim 11, wherein the plurality of peaks of theundulating configuration are within a common plane.
 13. The system ofclaim 11, wherein at least one peak of the plurality of peaks of theundulating configuration is located in a first plane which is differentthan a second plane in which at least one other peak of the plurality ofpeaks is located.
 14. The system of claim 10, wherein the distal portionof the lead body is configured to assume an undulating configurationincluding a plurality of peaks including the one or more peaks of eachdefibrillation electrode segment of the set of defibrillation electrodesegments, wherein the plurality of defibrillation electrode segments aredisposed to cover at least a portion of the plurality of peaks, andwherein the two or more electrodes are disposed to cover a portion ofthe undulating configuration between consecutive peaks of the pluralityof peaks.
 15. The system of claim 10, further comprising a conductordisposed within the lead body, wherein each defibrillation electrodesegment of the set of defibrillation electrode segments is electricallyconnected to the conductor.
 16. The system of claim 15, furthercomprising a connector disposed at the proximal end of the lead body,wherein the connector is configured to electrically couple with a pulsegenerator, and wherein the conductor is coupled to the connector. 17.The system of claim 10, wherein the set of defibrillation electrodesegments includes a first defibrillation electrode segment and a seconddefibrillation electrode segment, wherein the lead further comprises: afirst conductor disposed within the lead body and electrically connectedto the first defibrillation electrode segment; and a second conductordisposed within the lead body and electrically connected to the seconddefibrillation electrode segment.
 18. An implantable medical electricallead comprising: a lead body defining a proximal end and a distalportion, wherein the distal portion of the lead body extends along alongitudinal axis; a first defibrillation electrode segment disposedalong the distal portion of the lead body, wherein at least a portion ofthe first defibrillation electrode segment is configured to assume afirst curved shape comprising a first one or more peaks displaced fromthe longitudinal axis; a second defibrillation electrode segmentdisposed along the distal portion of the lead body, wherein at least aportion of the second defibrillation electrode segment is configured toassume a second curved shape comprising a second one or more peaksdisplaced from the longitudinal axis; and two or more electrodesdisposed on the lead body, wherein the two or more electrodes areseparate from the set of defibrillation electrode segments, wherein eachelectrode of the two or more electrodes is disposed along thelongitudinal axis of the lead body, wherein a length of the firstdefibrillation electrode segment is greater than a length of eachelectrode of the two or more electrodes, wherein a length of the seconddefibrillation electrode segment is greater than a length of eachelectrode of the two or more electrodes, and wherein the two or moreelectrodes are configured to perform at least one of: deliver a pacingpulse to a heart; or sense cardiac electrical activity of the heart.